There are many environments where air quality is insufficient for respiration due to insufficient oxygen concentration and/or contamination by unsafe particulate or gaseous matter. Yet, in these environments, it is important to be able to function normally in order to perform certain tasks. An example of this type of environment is a smoke-filled building which must be navigated by firefighters in order to render buildings safe as well as to rescue persons who may be trapped in this environment. Another example of a contaminate-rich environment may include a structure that has been overcome by a gas which may be harmful. This may occur, for example, during a military operation where adversaries release a toxic or otherwise unsafe gas to prevent capture.
There have been many advances in breathing apparatuses that have assisted functioning and respiration in these environments while tasks are performed. One example is a self contained breathing apparatus (SCBA) which is a wearable apparatus that includes a cylinder of compressed air, pressure reducer, lung demand valve (LDV) and a mask capable of maintaining a positive pressure therein. A SCBA apparatus provides a high degree of protection in view of its dedicated supply of compressed air in conjunction with the mask maintaining a positive pressure thereby forcing any contaminates that may enter the mask via a leak or incomplete seal out of the mask. A drawback associated with the SCBA apparatus is the storage capacity of the cylinder retaining compressed air. These cylinders have a finite capacity and, in environments of high stress, respiration increases thereby depleting the compressed air at a higher rate and potentially placing the user in danger of lacking breathable oxygen.
Another example of breathing apparatuses are negative pressure respirators which have masks that include at least one type of filter but which maintain the mask in a negative pressure state. These masks typically include air purifying respirators (APR) or powered air purifying respirators (PAPR) that selectively filter contaminates from the air as the person wearing the mask inhales. In operation, the user creates a vacuum inside the mask, by inhaling, to draw in air from the outside, through the filter. While different filters can protect against different contaminates in the air, these filters cannot protect a user from oxygen deficiency in the air. Only a SCBA apparatus with its own dedicated supply of air can protect a user against oxygen deficient air. In the case where the negative respirator includes a PAPR, the battery powered PAPR draws air through the filters and provides the power-filtered air through a breathing hose and into the user's mask. However, as the mask remains in a negative pressure state, any air flowing into the mask and not inhaled by the user will flow freely out from an exhalation valve in the mask.
Another device attempts to combine the SCBA apparatus, a PAPR device and a mask that may operate in one of a negative pressure mode or a positive pressure mode. This allows the user to breathe in filtered contaminate-free air and also provide the added protection of having a dedicated supply of clean compressed air in case the user finds themselves in a suddenly oxygen deficient environment. However, a drawback associated with this type of apparatus is the apparatus must be manually switched from a negative pressure state to a positive pressure state. Since a user needing to make the switch is likely in a compromising and difficult setting, any time delay associated with switching sources of air to a mask could have severe consequences for the user wearing the apparatus as well as those the user is charged with protecting.
Thus, a need exists to provide a breathing apparatus that automatically switches a mask from negative pressure to positive pressure to enable the user to breathe from a dedicated supply of compressed air without any delay. An apparatus according to invention principles addresses deficiencies of known pressure control apparatus.